The present invention relates generally to a minimally invasive approach to perform transesophageal cardiovascular and mediastinal procedures. More specifically, the invention relates to implementing the concept of transesophageal access to the heart, great vessels and related structures. The invention describes devices and methods to create a transesophageal access to the heart and surrounding structures to perform a body of surgical procedures within a beating heart and on other surrounding structures.
The access to the human heart has always been a source of active research especially recently with the advancement in technology that has led to improved management of cardiovascular pathology. Heart disease is the leading cause of death connected to all age groups in the United States. The esophagus has a close proximity to the heart and posterior mediastinum, which has allowed the use of transesophageal fine needle aspiration and transesophageal biopsy techniques to be used extensively in recent years to obtain tissue samples. Most of the posterior mediastinal tissues are accessible for biopsy including the lungs and lymph nodes. The technique has proven to be safe and reproducible with minimal complications. The microbial flora of the human esophagus is similar to that in the pharynx, which results in no bacterimia with transesophageal puncture using needles up to 1 mm in diameter in many studies. The esophagus has never been used to access the human heart, but rather to perform procedures related to the heart due to the close anatomical proximity. A number of trials have been described as in U.S. Pat. No. 6,120,442 for transesophageal intracardiac pressure measurement, in U.S. Pat. No. 5,417,713 for using a transesophageal defibrillating system, and in U.S. Pat. No. 5,179,952 for the use of a transesophageal electrocardial stimulator. Some trials were made to use the trachea for monitoring the heart as in U.S. Pat. No. 5,080,107 that describes the use of an endotracheal sensor for cardiac monitoring.
Access to the heart has always been the main determinant of the form, degree and invasiveness of therapy, which determines the ultimate success of the treatment modality. The left side of the heart is more systemically important and much less accessible than the right side for its anatomic location and the high blood pressure it generates in the systemic circulation. The spectrum of disease states that can be assessed diagnostically or therapeutically are generally more reflected on the left side of the heart. This is evident clinically in a wide range of cardiovascular pathology e.g. congestive heart failure. There is no known non-invasive method that can directly measure the pressure in any chamber of the heart. All current methods either use speed of blood flow as a non-invasive reflection of chamber pressure or they measure the pressure invasively via a catheter inside or near the chamber. The most common technique to measure the left atrial pressure is the pulmonary catheter wedge pressure method. The left atrium is a low-pressure, left-sided structure that has a special importance with regard to its mechanical and electrical properties. Unfortunately, there is no simple non-invasive way of directly measuring the left atrial pressure. Even with invasive measurement as in pulmonary artery catheterization, the measured value reflects an indirect estimation of the left atrial pressure, and thus can be inaccurate in many instances. The left atrium is also important in terms of electrophysiological mapping and ablation. The current techniques access the left atrium using a catheter indirectly from the right atrium across the inter atrial septum or in a retrograde approach through the aorta. Both techniques have their inherent side effects and complications. Thus, access to the left atrium is a described objective in order to treat a large subset of patients, such as congestive heart failure patients.
A second subset of cardiac patients in which the access to the heart is the main determinant of interventions and management are patients with congenital cardiac defects like ASD, VSD and PDA. The main pathology in most congenital cardiac defects is the presence of an unnatural conduit that shunts the blood from the right to left heart or the reverse. This overloads the side with lower pressure and any tissue or vascular bed in the shunted circuit. The pulmonary vascular bed is commonly affected by blood overflow that may lead to reversible or late irreversible pulmonary vascular hypertension. The in vasiveness of the current techniques limits the early implementation of a shunt closure especially in children, which is a curative intervention if done before irreversible vascular changes. Other techniques use the catheter transvascular approach with limited success due to lack of control and torque at the end of a long flexible, narrow catheter used in the procedure.
In a third group of patients, cardiac arrhythmias are responsible for a high percentage of morbidity and mortality. Atrial fibrillation is a common and chronic disease with a prevalence of 2-3% in the United States. The disease is longstanding and mandates chronic anticoagulation as part of the treatment to prevent any embolic disease especially to the brain. Chronic anticoagulation in itself carries serious risk of internal bleeding added to the toxicity of chronic anti-arrhythmic medications used to stabilize atrial fibrillation. Recently, surgical curative techniques have been described in the literature to treat atrial fibrillation. Access to the heart has been a main determinant in the use of any of these techniques. The invasiveness of the open chest approach has limited the number of the Maze-like procedures used to radically prevent the fibrillation impulses from being conducted to the ventricles. Also, the catheter-based approach is inaccurate, tedious, time consuming (up to 12 hours) and not definitive in creating enough linear ablations to prevent impulse conduction. The thoracoscopic approach is easier than the catheter-based transvascular approach but the side access to the posterior heart limits the linearity of ablation especially around the entrance of the pulmonary veins, which results in incomplete Maze, and recurrence of the disease. The three known accesses to the heart namely, the open chest, the catheter-based transvascular, and the thoracoscopic approaches suffer from serious limitations and complications which, in turn, limit the therapeutic options for most of patients. The limitations of the current three known accesses to the human heart can be classified as follows:
Most cardiovascular procedures are performed by opening the chest wall either by gross sternotomy or by lateral thoracotomy. The sternotomy approach is more common than the lateral thoracotomy as it allows greater field for the surgeon to introduce surgical devices, to control target tissues and to clamp and catheterize the aorta for induction of cardioplegia and bypass. It involves opening the sternum using a saw to cut through the bony structure. It also involves arresting the heart by cardioplegic techniques. The circulation is switched to cardiopulmonary bypass for preserving tissue perfusion. The above advantages of the stemotomy approach are offset by serious disadvantages. First, the risk of stopping the circulation with the possibility of causing marked decrease in tissue perfusion or ischemic damage that may involve vital tissues like the brain, heart or kidneys. Second, the risk of embolization of dislodged tissues in the aorta due to aortic manipulation including clamping and catheterization. The dislodged emboli can cause acute brain or peripheral ischemia. Brain damage may be permanent after an embolic event during open sternotomy approach. Even without any embolic or gross brain injury, psychometric analysis shows definite changes and cognitive defects in young healthy individuals after open-heart surgery. Third, opening the chest wall by cutting through all layers including the bony sternum with great force applied for rib retraction produces significant pain after the surgery with post surgical morbidity and, if severe, mortality. The post surgical wound care and pain may require rehabilitation in complicated cases with longer hospital stays and increased expenses. Fourth, concomitant morbid states or age extremes may adversely increase all of the above-mentioned risks.
The other two methods to access the heart are the transvascular and the thoracoscopic approaches. Both have the advantageous difference from the conventional open-chest approach in not requiring gross thoracotomy. The thoracoscopic approach may or may not involve cardioplegia and cardiopulmonary bypass. Again, these procedures have fundamental disadvantages.
For the transvascular approach to the treatment of heat defects, the disadvantages are inherent in the fact that the procedural tools have to go through and stay in a blood vessel or a cardiac chamber. Thus, the tools can only be long, narrow, flexible catheters. This affects the controllability and the force generation at the tip of the catheter which, in turn, decreases the accuracy and precision of the procedure. The access to the heart is mainly from the right side and rarely through an aortic retrograde approach. To reach the left heart, a septostomy opening is made in the interatrial septum that decreases the control over the catheter and makes the manipulation of the catheter tip more difficult as the catheter has to pass through the narrow right atrium and the small septostomy opening. Another main limitation is the caliber of the lumen of peripheral vessels through which the catheter has to travel. This is even a more limiting factor in young children whose smaller vessels raise the risk of vessel injury that may be acute, such as intimal dissection, or chronic such as major vascular obliteration and fibrosis. In the elder population, the occurrence of peripheral fat embolization is another risk for manipulations of a catheter in the aortic lumen for procedures like coronary angiography. This may result in temporary acute or chronic ischemia to the lower or upper extremities.
In addition to vascular injury, some techniques like intracardiac mapping and ablation require the passage of large catheters to be able to deliver large energy output through large electrodes. These ablative techniques are useful in cardiac dysrrhythmias as ventricular or supraventricular tachcardias and atrial fibrillation. A number of trials to apply mapping and ablation technique through the use of the transvascular approach have been described as in U.S. Pat. Nos. 4,960,134, 4,573,473, 4,628,937, and 5,327,889. In U.S. Pat. No. 6,047,218, a technique for ablation and visualization of the intracardiac chamber through the transvascular approach is described. The small size of the vessels limits the size of catheters used in ablation techniques. That limitation gives rise to a lack of control and positionability due to the flexibility, increased distance and decreased force at the tip of such catheters.
The transvascular approach has a limited use in surgical procedures like septa defect repair by using an introductory device due to the above-mentioned limitations. A number of trials to use the transvascular approach to deliver a patch from a vein via the right heart to close a septal defect have been contemplated; see e.g. U.S. Pat. Nos. 3,874,388; 5,334,217; 5,284,488; 4,917,089, and 4,007,743. In addition to the above-mentioned limitations, the use of patches to close a septal defect using the transvascular approach with lack of distal force at the delivery tip may result in inadequate fixation of the patch to the defect plus the inability of patch repositioning after its application to the defect site. The detachment of the patch from the defect site may lead to serious patch embolization and failure of repair. In some cases this may, in turn, require an open sternotomy to correct the failed transvascular repair.
The thoracoscopic approach provides more advantages over the transvascular approach in terms of having more control over the procedure tools, and increased precision in positioning the catheter tip to perform intracardiac procedures. The disadvantages of such approach can be considered. The inaccessibility of the posterior aspect of the heart to the rigid scopes passed from either side of the heart, which is mandatory to create an atriostomy opening in the posterior aspect of the atrium, is a problem. This may be solved by applying a stitch to the pericardium and pulling the pericardium to rotate the heart and expose the posterior aspect. The stitch should be applied from an anterior, not side, position to have enough rotation force on the pericardium. However, due to the narrow intercostals spaces in the anterior rib aspect, it is difficult to make such a stitch which makes the posterior aspect of the heart a difficult area to access. Another limitation is the need to have a second monitoring system to assess catheter position and convey accurate measurements as the procedure is not performed under direct visual examination. Such monitoring devices make the approach more complicated, may lack accurate precision, and may need to be invasive, e.g. removal of the fourth rib for visualization, or add a potential risk of ionizing radiation exposure with CT scanning, or be cumbersome and slow with MRI scanning, adding to the complexity of the technique. Second, the limited windows between the ribs as a limiting border from above and below the access, the surrounding intercostals muscles and underlying vital structures including the lungs, pleura, nerves, and great vessels can limit the access specially in young children with narrow intercostals spaces, and patients with deformities.
The need to access multiple intercostal openings to use a plurality of thoracoscopes counteracts the main objective of the technique to be minimally invasive and may turn out to be more invasive and cause significant tissue damage as it may also require removal of the fourth rib. The need to deflate the lung to widen the surgical field adds to the invasiveness and increases the complication potential of the procedure. The inability to explore the posterior mediastinum and related structures on the posterior aspect of the heart as the catheter is advanced from an anterior position makes procedures involving the posterior aspect of the heart less accessible as in ablation around the entrance of the four pulmonary veins in the left atrium. Indeed, the thoracoscopic approach has been criticized lately by a number of studies that show numerous post-surgical complications. A number of trials to perform surgical intracardiac procedures from the thoracoscopic approach have been described, e.g. in U.S. Pat. Nos. 5,980,455; 5,924,424; 5,855,614; 5,829,447; 5,823,956; 5,814,097; 5,797,960; 5,728,151; 5,718,725; 5,713,951; 5,613,937, and 5,571,215. Closed chest coronary bypass surgery using the thoracoscopic approach is described in U.S. Pat. No. 6,123,682.
None of the currently available techniques directly accesses the posterior aspect of the heart and coronary circulation or the posterior mediastinum. Recently, there has been heightened interest in minimally invasive methods of cardiac surgery that allows intracardiac or extracardiac procedures and avoid the need to crack the rib cage or stop the heart.
What are needed, therefore, are devices and methods to enable a new access to the human heart that is easily accessible, that allows access to both the interior and exterior of the heart simultaneously, with enough force and control over the procedure tools, that causes minimum tissue injury, and that can be applied to the heart, while still beating, without the need for general anesthesia. This access should allow the performance of surgical procedures like septal defect repairs, treatment of cardiac dysrrhythmias and treatment of various cardiac pathology such as valvular manipulations with a degree of success similar to the open approaches, while avoiding the complications and limitations of the above-mentioned prior techniques.
Accordingly, it is a principal object of the invention to provide method and means for providing a transesophageal access to the heart, great vessels, posterior mediastinum and all related structures.
The invention provides procedures that can safely and accurately create a transesophageal access into the heart, pericardium, posterior mediastinum, the great vessels and all related structures. The procedures can be carried out on a beating heart without the need for stopping the heart, cardiopulmonary bypass or gross or minor thoracotomy. This transesophageal access can be used to perform a variety of diagnostic and therapeutic procedures including but not limited to:
(1) Esophageal: manipulations, insertion of intra or extraesophageal devices to sense and control the electrical and mechanical properties of the esophagus and stomach; transesophageal electrical cardiac pacing, mapping and ablation; dual combined stereoscopic 3D ultrasound imaging of the heart from the transesophageal and intracardiac positions;
(2) Posterior mediastinum: insertion of mediastinal devices for chronic sensing and control of electrical, chemical, mechanical, genetical, pharmacological, and physical manipulation of tissues in the posterior mediastinum and related structures such as lymph nodes, lungs, nerves, vessels, heart, esophagus, diaphragm and stomach; posterior mediastinal electrical cardiac pacing, mapping and ablation;
(3) Pericardium: accessing the pericardial space for assessment and control of intrapericardial electric, mechanical, physical, genetical, pharmacological and chemical properties, aspiration and biopsy of the pericardium or pericardial effusions, excision of the pericardium, pericardiotomy, or pericardial tumor removal; epicardial ultrasound; pericardial assessment of intracardiac chamber pressure, insertion of a sensor to chronically perform a variety of functions as will be mentioned in detail in one of the preferred embodiments of the invention; insertion of intrapericardial catheters for electrical, chemical, mechanical, genetical, or pharmacological interventions; extracardiac transmyocardial laser revascularization; extracardiac electrophysiological mapping and ablation; extrapericardial myocardial assist device insertion and manipulations;
(4) Intracardiac: intracardiac imaging including intracardiac endoscopy, intracardiac ultrasound; repair of valvular diseases such as mitral valvotomy, excision or laser evaporation of vegetations, laser vavuloplasty of the mitral, tricuspid or the aortic valves; laser transmyocardial revascularization; electrophysiological mapping and ablation for treatment of most arrhythmias including atrial fibrillation; repair of congenital abnormalities as ASD, VSD, PDA; anterograde, retrograde, transmyocardial or transepicardial coronary manipulations, revascularization, and bypass of intraluminal obstruction; septal myotomy; endomyocardial biopsy; insertion of intracardiac transient or permanent assist devices; and various other intracardiac procedures that can be performed transesophageally while the heart is beating;
(5) Great Vessels: pulmonary thrombectomy and revascularization, repair of congenital abnormalities such as PDA and transposition of great vessels; sensing and manipulation of venacaval, aortic, pulmonary arterial and pulmonary venous pressures; insertion of transient or permanent intra-vascular diagnostic and therapeutic devices such as catheters, sensors, drug-delivery vehicles, imaging probes, stents, balloons and the like.
In a first aspect of the invention, a tubular intraesophageal device, to wit: an access main unit (AMU) is provided for accessing the lumen of the esophagus, disinfecting the surface mucosa through special porous channels, isolating a long segment in the esophagus behind the heart, blocking any secretions from above or below the segment by inflating an elongated balloon, maintaining sterilization of the isolated segment by establishing a continuous suction-irrigation circulation between the outside surface of the AMU and the esophageal mucosa. The AMU includes an elongated flexible tubular body configured to extend through the esophagus from the pharynx to a predetermined distance below the middle third of the esophagus and above the gastro-esophageal junction. The AMU has an open area on its outside surface, denominated the access exit field (AEF), to allow for creation of the access through the esophageal wall. The AMU contains a plurality of elongated tubular lumens of specific dimensions to allow for the passage of various elongated flexible devices or tools to be described. These lumens include the intraesophageal longitudinal lumen (ILL) that is a collapsible, double layered, wide lumen, open from both ends, and extends from the proximal end to beyond the distal end of the AMU. The ILL can carry an ultrasound probe for procedure monitoring and creation of a 3D stereoscopic ultrasound image of the heart and surrounding structures after the addition of the intracardiac image from an intracardiac ultrasound probe as mentioned below.
A second lumen of the AMU is the transesophageal access lumen (TAL) which is a longitudinal tubular lumen that extends from the proximal end of the AMU and travels across its length to make a 90xc2x0 angle at its lower end and exits perpendicular to the main axis of the AMU in the center of the AEF. The TAL carries elongated flexible devices including a access side unit (ASU) that penetrates through the esophageal wall and creates an access to the desired target area outside the esophagus. A third tubular lumen inside the AMU is the suction lumen (SL) used to create a negative pressure in the space of the AEF between the outer surface of the AMU and the esophageal mucosa. The SL also allows for suctioning of any secretions that may escape into the AEF.
According to the invention, the ASU which passes through the TAL is made of two concentric, slidable, small flexible tubes open at both ends. The outer tube is a sheath like tube that contains small parallel longitudinal tubules along the thickness of the sheath. The tubules are open at the proximal ends. At the distal end, each tubule has a flap at its distal end that is level with and below the outer surface of the sheath. Each tubule carries a flexible distal-hooked needle extending from the proximal end of the tubule and curving laterally inside the flap at the distal end thereof the proximal ends of needles are geared to a dial at the proximal end of the ASU so that the needles can be rotated to move the flaps between retracted and radially extended positions.
The inner tube of the ASU has two separate longitudinal lumens. A smaller lumen carries an endoscope for direct visualization and monitoring of the procedure. A larger lumen may carry various elongated flexible devices to be described for performing selected extra and intra-cardiac procedures. The tip of the ASU has an umbrella with a plurality of supporting flexible, resilient, radially arranged wires and a suitable material extending between the wires to seal the penetration in the esophageal lumen. Each wire carries a knob that can receive and irreversibly attach to the distally hooked needle and the knobs are attached to the ends of suture threads. The threads are coiled on the inner surface of the umbrella and each thread is attached at both ends to two adjacent knobs. This allows the creation of a purse string suture around the distal end of the ASU after penetration through the esophageal lumen by penetration means to be described. The smaller and larger tubes of the ASU are beveled at their distal ends so that the penetration means is tapered along the bevel""s at of both ends. The penetration means can be retracted into the inner lumen of the ASU after they are advanced through the esophageal wall.
As just stated, the ASU may include penetration means within its inner lumen to penetrate through the esophageal wall. The penetration device may be a needle with overlying dilator, surgical blade, electrosurgical blade, laser blade or any other conventional penetration means. Preferably, the penetration means is beveled in line with the smaller lumen of the inner ASU tube.
The apparatus also includes a transesophageal intracardiac access (TIA) which is similar in structure to the ASU but smaller in diameter to fit inside the larger lumen of the ASU. It can create an opening of 6 mm or more in a cardiac chamber. The TIA allows the passage of elongated flexible devices to the interior of the heart to perform various procedures. In a preferred embodiment, the TIA uses an umbrella at its distal end to seal the penetration through the cardiac chamber wall and to make a purse string suture that is used at the end of the procedure to secure the penetration site. In another embodiment, the sealing means at the distal end of the TIA can be an inflatable balloon, double balloons, or an expandable flange. The short length and wide diameter of the TIA allow for the precise positionability and control of the intracardiac devices.
The TIA may also include a penetration device within its inner lumen to penetrate through the muscular wall of a cardiac chamber. The penetration device may be a needle with overlying dilator, surgical blade, electrosurgical blade, laser blade or any other penetration means. The penetration means can be retracted into the inner lumen of the TIA after it is advanced through the muscular cardiac wall.
The TIA may also include a valve for hemostasis in the inner lumen to prevent blood back flow inside the lumen of the TIA after opening a penetration to the interior of the heart. The valve may be located at the proximal end of the TIA or more preferably at the distal end thereof. The TIA can then be flushed across the hemostatic valve with normal saline to create a blood-saline interface to avoid air bubbles in the lumen of the TIA. If the TIA is positioned in a low pressure chamber like the right or left atrium, the back-pressure of the blood my be low enough to obviate the need for a valve mechanism in the blood-saline interface. After the placement of the TIA inside a cardiac chamber, preferably the left atrium, a wide, short and almost straight access is created from outside the body across the esophagus into the left atrium that allows various devices to be described to perform diagnostic and therapeutic procedures.
Using the TIA mentioned above and in a preferred embodiment, the invention provides devices and methods to repair atrial or ventricular septal defects. The method of repair may include direct purse string closure of a septal defect using an elongated flexible device introduced through the lumen of the TIA and positioned at the septal defect with the aid of either direct endoscopic visualization, intracardiac ultrasound imaging, or combined transesophageal and intracardiac ultrasound stereoscopic imaging as described below. Advantageously, the purse string flexible closure device fixes its working tip to the outer edge of the defect after passing through it by means of a retractable umbrella at said tip. This is a unique way of closure as it uses semi-continuous purse string suturing on a flexible and controllable device. The frame of the umbrella may hold a non-thrombogenic material between its collapsible wires, like polyester or polytetrafluorethylene, to temporarily close the defect and record the hemodynamics of the heart to predict the burden of pressure changes inside the heart. The wires of the umbrella are radially arranged and made of a flexible but resilient material such as the material trademark Nitinol(trademark), to be able to pass through the TIA and deploy on the distal aspect of the defect.
The suturing device is similar to the TIA in structure but need not have the wires of the distal umbrella covered with a patch as it is optional to test the hemodynamic effect of the defect closure as mentioned above. The flexible purse string-suturing device (FPSS) is made of two sliding flexible tubes sharing the same longitudinal and transverse axis and sliding on one another. The outer tube of the FPSS constitutes a formed with longitudinal tubules with distal flaps and containing distally curved needles just as in the ASU described above. The proximal ends of the needles carry spur gears which mesh with a ring gear in a dial extending around the proximal end of the FPSS. The distal end of each tubule leads to a groove on the corresponding flap. As with the ASU, the flaps are in level with the wall of the sheath when in their normal or horizontal position. By turning the dial, the needles may be rotated so that their turned distal ends more flaps to think radially extended positions.
The inner tube of the FPSS is an elongated flexible tube with proximal and distal ends and a central lumen. It slides tightly inside the outer sheath on the same transverse axis and has a longitudinal groove(s) on its outside surface that slidably receives a matching protuberance(s) extending from the inner surface of the outlying sheath. At its distal end, the inner tube of the FPSS has an array of wires arranged around the distal opening of the tube in an umbrella-like fashion. These wires are collapsible, flexible, and resilient. Each wire moves around an elbow on its connection with the rim of the distal end of the tube. A deploying mechanism such as a spring, coil or similar means connected to the distal end of the tube and the proximal end of each wire, works to deploy is and thereby extend the wire perpendicular to the longitudinal axis of the inner tube of the FPSS. The wires are coupled to a set of controlling threads connected to their inner aspect immediately above the elbow connection with the tube. The controlling threads run in grooves in the thickness of the inner tube. By exerting tension on the controlling threads, the wires may be retracted against the deploying mechanism to their original non-deployed flat positions. Advantageously, this technique allows the wires to be re-retracted and re-deploying for appropriate positioning. In the non-deployed state, the wires are parallel to each other and to the long axis of the tube and lay level with the surface of the inner tube. Upon deployment, the wires fan out and are generally perpendicular to the tube.
Each wire carries a knob on its inner aspect. The knob is a hollow structure that captures the tip of a hooked needle. This fitting forms a one-way coupling by means of the shape of the undermined lumen. Each knob is connected to one end of a thread, while each two adjacent knobs are connected by one thread. Thus, if the FPSS has 8 wires at its distal end, and each wire carries a knob, this means that there are 4 continuous threads carried by the 8 knobs.
In one procedure according to the invention, the FPSS is passed towards a septal defect. The distal end of the device is passed into the heart chamber on the side of the cardiac septum distal to the point of introduction, e.g., the right atrium if the device has been introduced through the left atrium across the defect and the wires are deployed to a perpendicular position on the distal end by means of a deploying mechanism that can be reversed later. The wires may be out radially by decreasing the tension on the controlling is threads, and releasing the deploying mechanism.
The FPSS may be pulled back slightly so that the wires are flat with the outer surface of the septum while the lumen of the device is inside the defect. The wires are now on one side of the defect while the sheath or outer tube is on the other side. By turning the aforesaid dial on the FPSS 90xc2x0, the flaps may be moved to extended positions perpendicular to the sheath. The needles are pushed down in the grooves by means of a plunger or similar device. The outward groove in each flap directs the needle in that flap to extend in a fixed direction. The needle penetrates the septum around the defect at a predetermined distance away from the center of the device that allows the needle""s hooked tip to reach inside the undermined lumen of the knob carried on each wire on the other side of the septum.
The needles are thus tightly coupled to the knobs on the wires and hence to the thread attached to the knobs. The needles may be withdrawn back across the septum into the corresponding flaps of the outer sheath. The dial on the outer sheath may then be rotated back return the flap to their original retracted or horizontal positions and the whole sheath with its needles may be withdrawn outside the body. The threads are long enough to come out from around the septal defect, coupled to the tips of the needles. The threads may then be cut just below the connection with the needles leaving the physician with either 4 or 8 thread ends depending on the kind of FPSS used.
In a preferred embodiment of the invention, a device to tie the threads together comprises a thin sheet of Vicryl or similar absorbable material, to connect two ends of the threads together by compressing the sheet of Vicryl to form a tight cylinder around both ends. Knotting, gluing, or similar means can also accomplish the tying. By connecting the ends of consecutive threads together, a continuous loop of thread is formed in the shape of a purse string suture loop. The inner tube of the FPSS is pushed slightly into the defect to allow the controlling threads to retract the umbrella wires to the original flat non-deployed state. After retraction of the wires, the inner tube of the FPSS is withdrawn from the defect through the TIA to outside the patient""s body. By pulling the two terminal ends of the purse string suture loop, the suture tightens and the defect is closed. The two ends are then tied together to form a knot, and the knot is pushed down by a flexible elongated knot-pusher that may be pushed down the lumen of the TIA.
The same technique described above can be used to close the esophageal and cardiac penetration sites formed by the ASU and TIA, respectively. This suturing technique is described for exemplary purpose only. The method of the invention can be used for any catheter-based purse string suturing intervention.
The lumen of the FPSS) may also carry an imaging element for accurate positionability, monitoring and validation of the closure of the defect. This imaging element can be an endoscope with a balloon on the distal end to allow visualization through blood or with a CCD chip to create an image reflected through blood as described in the prior art. The imaging element can preferably be an ultrasound probe that is either used alone or in combination with the transesophageal probe in a synchronized fashion to create a 3D, stereoscopic ultrasound image. The synchronization can be accomplished in one of two ways. The first is to use two probes with two separate energy sources. Each probe acquires images separately and also acquires information about its own position with regard to the heart from the other probe. The probes alternate with high frequency to produce signals to avoid noise and distortion. The second method is having the signal produced by one probe received by the other probe in a continuous fashion. In this case, both probes can split one energy source and one receiver. The signals representing the images from both probes are fed to a multiplexor for image registration and then to a microprocessor for reconstruction. This allows for the creation of a 3D image of the area examined by moving the probes from two different orientations. The image can be displayed on line or stored for later processing. The technique of creating 3D ultrasound images can be achieved using the transesophageal probe alone by having two ultrasound transmitter/receivers spaced apart by a changeable distance so that the signal produced by one transmitter is received by the distant receiver and vice versa. By positioning one transmitter receiver in a distal position such as in the stomach and the other in a proximal position such as in the esophagus, a combined stereoscopic ultrasound image can be created. The stomach transmitter/receiver unit can be tilted and moved away or towards the esophageal unit to create a more detailed image of the heart from various locations.